Updated 26 March 2013

Your anus

Often regarded as taboo, erotic, and many times, used as an offensive term, the primary purpose of the anus is for defecation, better known as pooing.

Bottoms up. But this is not your average toast. This is the anus. Often regarded as taboo, erotic, and many times, used as an offensive term, the primary purpose of the anus is for defecation, better known as pooing.

The anus is a 1½-inch canal located at the lower end of the rectum, between two rather rounded, muscular pieces of meat, the buttocks. It contains two sphincters, one being external and the other one internal. This prevents you from having a rather unpleasant smelling leak while in the cinema, or worse, while having dinner with your in-laws.

The internal sphincter is a muscle that has an involuntary action, whilst the external sphincter works on voluntary action.

Pass the toilet paper
Nature calls, and it is finally time to drop everything else and run for the loo – or as it is also called, dropping the kids off at the pool, losing a few grams, or seeing an old friend off to the coast. When the rectum is full, pressure is forced along the anal canal to allow the walls to part. The rectum then shortens as it fills with excrement, and peristaltic motions push the faeces out. The internal and external sphincters then allow the faeces to be passed out.

But do not push too hard. And do not sit longer than the time required.Haemorrhoids, also known as piles, are often the result of this.

Keep it clean
Since the anus is responsible for expelling unwanted matter from the body, one can imagine that it is not the cleanest place on the body, and therefore needs to be looked after. One should use soft, non-scented toilet tissue to clean the anus after sitting on the throne. Rough, scented toilet tissue will only lead to irritations and could make your day quite nasty. And maybe also quite nasty for everyone around you.

When bathing, only wash the anus with a mild soap and hot water. Do not scrub it as it could cause skin irritations and will strip the anal area of its natural lubricants that keep it soft and supple.

Your own orchestra
Besides being used for defecation, the anus can also occasionally serve as a musical instrument.Flatulence or farting, as embarrassing as it might be, is part of everyday life. Flatulence is basically a mixture of different gases that are produced by bacteria and yeasts living in the gastrointestinal tract.

Some gases are flammable. Hydrogen and methane are the two gases that can catch fire. The foul odour resulting from a whistling experience is from butyric acid, sulphur and carbon compounds. Even invisible particles of faeces can be present in a fart. Although the anus does not produce these gases, the anus serves as an exit hole for these gases to be released.

The vibration of the anal opening is the cause for the noise when a fart is made. The sound will depend on the tightness of the sphincter muscle, the speed of the travelling gas, moisture, as well as body fat.

The urge to let rip is caused by the same peristaltic motions when faeces is pushed out, and nerve endings in the rectum can distinguish between faeces and gas. However, these nerves can become confused every now and then, which could be a good explanation for the skid marks in your underwear.

Banging on the back door
Since the beginning of time, the anus has also been accepted by many cultures as an erogenous zone, explaining the act of anal stimulation. The anal walls are rich in nerve endings that can give a feeling of pleasure. Many homosexual and heterosexual people practice this form of intercourse.

However, anal sex should always be practiced with a condom and a good water-based lubricant. It is very possible for the walls of the rectum to be torn either through a very solid stool, or by rough anal sex. This puts the receiver at a much higher risk of HIV, sexually transmitted infections, and other bacterial infections.

Interesting facts

The average human being can produce up to 1.5 litres of gas throughout the day

The hairs growing around the anus help keep the anus dry and prevent any harmful dust particles from entering the rectum

Ask the Expert

Dr Naayil Rajabally obtained his medical degree at the University of Witwatersrand in 2000. He completed his gastroenterology training in 2011 and subsequently completed his MPhil degree in Gastroenterology at the University of Cape Town. Dr. Rajabally has expertise and special interest in Crohn’s disease and ulcerative colitis.
This expert forum will be closed until further notice

posted on 11-03-2015

posted on 09-03-2015

posted on 05-03-2015

posted on 02-03-2015

posted on 25-02-2015

Still have a question?

Get free advice from our panel of experts

Your question

More detail

Your name (optional)

The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.

Get a daily health tip

Stay in touch

The information on Health24 is for educational purposes only, and is not intended as medical advice, diagnosis or treatment. If you are experiencing symptoms or need health advice, please consult a healthcare professional. See additional information.